To improve mold resistance and the buffering function of bottom by arranging a buffering member composed of a plate-shaped urethane foamed material interposing a buffer sheet inside the bottom of main body while sandwiching it, and making a lining around the main body of lid into gas permeable fabric.

A soft synthetic resin plate-shaped member 5 composed of the urethane foamed material, etc., arranged around the inside of lid 3 and main body 1 has a lot of regularly or irregularly opened small holes 6, provides a function for preventing the deformation of bag and provides a function as a gas permeable buffering member as well. Besides, at a position inside the bottom of main body, the buffering member is arranged while interposing the buffer absorptive sheet, which is sandwiched, arranging a lot of small bags sealed with air between the two layers of soft synthetic resin plate-shaped members composed of urethane foamed materials or the like. Roughly woven fabric, for example, is used for linings 1B and 3B as lining materials around the inside of lid 3 and main body 1 so that the bag providing gas permeable functions can be provided.